British Ambassador to Russia Tony Brenton leaves Moscow on Tuesday and will be replaced in early October by Anne Pringle, a former envoy to Prague, a source in the embassy said on Tuesday.

The outgoing diplomat, 58, has been the U.K.'s mouthpiece in Russia during a turbulent period in the countries' relations, plagued by spying rows, extradition demands from both sides, and the closure of British Council offices.

His replacement served as an aide to the British ambassador to the Soviet Union from 1980 to 1983. For the past three years Pringle has led the Foreign Office's Strategy and Information department, and between 2001 and 2004 she was ambassador to the Czech Republic.

The low-point of Brenton's four-year term came after he spoke at a conference organized by the Other Russia opposition coalition in late 2006. For the next six-months pro-Kremlin nationalist youth group Nashi reportedly stalked and threatened the diplomat, an experience he called "psychological harassment bordering on violence."

Brenton complained that when he went to the shops he would be hounded by abuse-hurling activists from Nashi ("our own"), and that eventually his wife and children felt under threat. He said the campaign continued for several weeks after the Foreign Office lodged an official complaint with the Russian authorities.

Since Brenton moved into the ambassador's residence across the river from the Kremlin in March 2004, Russia and Britain have been caught up in disputes over London's refusal to extradite fugitive ex-oligarch Boris Berezovsky and Chechen terrorist emissary Akhmed Zakayev, and Moscow's refusal to hand over Andrei Lugovoi, accused by London of murdering intelligence defector Alexander Litvinenko in London in late 2006.

Two years ago the Russian security service accused four British Embassy employees of using a roadside 'spy rock' packed with hi-tech transmitters to communicate with Russian double-agents, an incident harking back to the Cold War.

Brenton, whose role was focused on promoting diplomatic and cultural ties between the countries, saw tensions with the British Embassy's cultural arm, the British Council, gradually build up from 2005 over tax non-payment and status irregularities, culminating in the closure of the council's regional offices earlier this year.